Abstract: The basic property of three kind of UFA with different fineness prepared by super -fine grinding progress, the mechanical properties of cement mortar and concrete samples added with 10%of these kind UFA ,as well as the workability of concrete mixture were investigated .The results show that , the activity of UFA enhanced with the increase of fineness .Involving of UFA improved the workability of concrete mixture and the mechanical properties of mortar and concrete samples significantly .By using UFA and superplasticizer without silica fume , C80 high performance concrete was prepared .The results of micro-pore structure revealed that the volume of harmless pores inside the concrete samples CUFA 4 blended with UFA4 was larger than the samples of CUFA 2 and CUFA6 , which was in accordance with the macroscopical mechanical experiment results of concrete .

Key words: ultra-fine fly ash;concrete;workability;mechanical property